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CLASSIfied is a mission in South Park: The Fractured But Whole.
Simply head to Jimmy's House to begin with. A cut scene will then play, whereby CLASSi notices The New Kid's arrival and proceeds to call out Fastpass. He will then ask The New Kid to start interrogating CLASSi, though The New Kid remains silent as always. Fastpass then will claim that staying silent will make a witness antsy, however CLASSi is having none of this; she then states that she will provide the information about the missing cats once she has her prescription delivered, otherwise she won't be able to think straight as she claims.
After that, Fastpass will proceed to transport The New Kid upstairs to his room, whereby he has made the final preparations to his device: the DNA Fibulator. Proceed to stand under the DNA Fibulator, whereby Fastpass will explain that he has opened a DNA slot inside The New Kid's Artifacts app.
For this case, you will be given three DNA slots to begin with: High Pain Threshold, Inhuman Accuracy and Mutant Strength. Pick the DNA slot which suits best to your current equipped abilities, then proceed to exit your phone menu.
Once complete, Fastpass will proceed to turn off the DNA Fibulator; you may proceed to leave Jimmy's House, whereby the next mission will commence.